Rotary line switch



May s. 1928.

B. D. WILLIS ROTARY LINE SWITCH Patented May 8, 1928.

' NI E ST AUTOMATIC 'nnno'rmo INQ, or CHICAGO, ILLINOISQA conrona'rionor DELA- WAR Application filed May 9,

This inventionrelates in general to automatic switches, but is concernedmore particularly with switches of the automatic hunting type, commonlyknown as .line switches. Switches of this character are used inautomatic telephone systems, individual to each subscribers line, and;when used in this situation the. function of each line switch is toselect'a trunk to an idle succeeding switch, for example, a first selector, and connect the subscribers line thereto.

The object of this invention is to provide new line switches of therotary type having ahome or normal position inwhich theswitch wipersnormally rest. WVhen a call is initiated, the wipers are rotated in aforward direction in-search of a trunk to an idle succeeding switch, andcome to rest when they engage the contacts at which the conductorsot atrunk to an idle succeeding switch terminate. WVhen the call is overwithand the switches associated with. the talking connection arereleased, the wipers of the line switch are again automatically rotatedin the forward direction until they reach the homeposition. y

The utility and advantages of the homeposition type rotary line switchare commonly known to those familiar in the art, so no discussion ofthese subjects is given.

The new line switches which form the subject-matter of this inventionare illustrated by means ofthe-usual schematic cirouit diagrams in Figs.1 .and 2 of the accompanying drawing. Refer-ring to'this draw" ing, inFig. 1 is shown a subscribers tele phone substation A with a lineterminating at a central automatic exchange in the individual lineswitch LS, which is of the home position rotary type. At the banks ofthe line switch access is had to first selector switches. These selectorswitches may be of any well known type, the vertical and rotary, forexample, and are responsive. to the first digit dialled by the callingsub- SCl'lbGlC. One of these selector switches is indicated in Fig. 1 byreference letter S, only those elements having to do with the operationof the line switch being shownj A call from the substation A to anothersubscriber may be extended through line switch LS, selector S, andthrough other selectors, d ma-sing n th size at the y tem, an

v to protect this line from I being norms LINE swrrcn.

1925. Serial No. 28,995.

through a connector scriber.

switch to called sub In Fig; 2 is showna similar system; the

subscribers substation A, theline switch ranged to. operate with acommon inter- 'rupter I, wh leiin the line switch LS",t-he

stepp ng magnet has its individual inter-I rupter springs, andaccordingly,- I v Having given a general explanation of the 1nventionand the apparatus. involved, the operation of the equipment will nowbefexthecircuits are adapted plained more indetail. For this-purpose itwill; be assumed thatthe subscriber at substation A desires connectionwith some other subscriber 1n the exchange. To initiate" the PATENT FBERNARD n, wILLis, ior'onroaqo, inmnors esslonon, BYMES assrcirnimn'rs,To

call, the subscriber atsubstation A removes his receiver. Removing thereceiver at substation, A places a direct current bridge across thelineconductors 2zan'd 3, thereby 1 closing a circuit for the line relay 5 ofthe line switch LS. This circuit may be traced from the grounded restingcontact and armature 10, line conductor 3, through the substation A,line conductor 2, armature 7 and the resting contact, through thewinding of line relay 5 to battery; The wipers 23, 24, 25 arenormallyresting on the home-position contacts 20, 21, 22, respectively. Upon theenergization of'line relay 5, at armature l1 and the Workingcontactground is placed on the private normal conductor 16 connected to theprivate contact in the connector banks connected with by some othercallingline. A circuit is also completed from ground by way of rmaturel1 and the working contact, homeposition contact 21, wiper 24:, workingcontact and armature 12," through the lower winding ofthe switchingrelay 4 to battery.

The upperwinding of switching relay t is adjusted so that armature 12and its Working contact close before armature 11 and 1ts working contactclose. This is to assure the proper-partial operation of switching relay4 at this time. A circuit is now completed :for the stepping magnet 6from ground by way of armature 11 and the working contact, armature 9,contact springs 18 and 17,

through the winding of the stepping magnet 6, to the interrupter I.which supplies interrupted battery. The interrupter I, as indicated bythe small arrows to either side otthe conductor connecting theinterrupter to the magnet 6, is common to a plurality of linesi'vzitches such as LS. As long as this circuit is maintained complete,the stepping magnet will energize and deenergize in response tointerrupted battery from interrupter 1. The stepping magnet is arrangedto rotate the switch wipers on its return stroke, 'i. e., when itdeenergizes. the first deenergization of steppingmagnet (t the wipers23, 24, 25 are rotated oi? the home-position to the next set of bankcontacts. Cam 14 also rotates and closes springs 13 thereby preparingthe return stepping circuit to be described later. If thefirst selectoraccessible at this set of contacts is busy, there will be ground on theprivate contact engaged by the private wiper 24 and the ground will bemaintained on the junction of the upper and lower winding of thestepping relay 4. The circuit for the stepping magnet 6 is stillmaintained and on the next dcenergizationot the magnet the wipers willbe rotated to thenextset of bank contacts. This stepping action willcontinue until the wipers 23, 2 t, 25, engage a set of contacts leadingto an idle selector switch, the. idle condition being indicated by noground present on the private contact.

It will be assumed that selector S, accessible at the line switch bankcontacts 26, 2?. 28. is the first idleselector found. Under thiscondition there is no ground on bank contact 37 and the upper winding ofswitching relay 4 is no longer shortcircuited and the relay willenergize completely. In op-v erating fully, armature 9 completes itsstroke, separates springs 18 and 17 and makes contact with both springs18 and 19. The circuit of the stepping magnet is thus opened and as aresult the wipers 23, 24, E remainengaged with'the bank contacts leadingto selector .The complete energization of switching relay 4 also resultsin the opening of a point in the return-stepping circuit, to bedescribed later, at armature 8, and in the operation of armatures 7 and10 which disconnects theline conductors 2 and 3 from the line relay 5and ground, and connects themby way of wipers 23 and 25, bank contacts26 and 28, armatures 33 and 35 andthe resting eontacts,through the upperand lower windings of the line relay 31 Upon of the selector S tobattery and'ground, rcspectively.

The line relay 31 ot' the selector S energizes overthe above tracedcircuit and closes acircuit for the release relay 32 atarmature Releaserelay 32 operates and places ground on conductor 38 at arn1ature37thereby supplying a holding ground for the switching relay shot the lineswitch LS and a protecting ground to conductor 16, by way or bankcontact 27 and wiper 24:, before line relay 5 has had time to fall back.

The subscriber at substation A now dials the directory number of thesubstation with which connection is desired. Inresponse to the firstdigit dialled, the selector S raises its wipers to the proper level ofbank contacts, corresponding to the digit dialled, and then rotates itswipers in search of'an idle trunk to a succeeding selector. In responseto other digits dialled by the calling subscriber, other selectorsoperate in the well known manner, the number of selectors beingdetermined by the size of the system. The operation of the succeedingswitches-is well known in'the art and consequently need not bedescribed. Responsive to the last two digits dialled, a connector *aisesits wipers and then rotates them to connect to the called line,automatically signals the called subscriber and finally completes thetalking connection when the called subscriber answers. The subscribersmay then hold conversation.

At the termination of the conversation the subscribers will replacetheir receivers on their respective switch-hooks. Replacing the receiverat substation A opens the direct current bridge across the lineconductors 2 and 3. As a result, the selectors are released, in the wellknown manner, and the holding ground removed from conductor 38. Theswitching relay 4: deenergized and its armature springs are restored tonormal. A return-stepping circuit is now completed for the steppingmagnet (3 from ground by way of arnniiture 11 and the resting contact,closed springs 13. the resting contact and armature 8, closed springs 18and 17, through. the winding of the step ping magnet 63, to theinterrupter I which supplies interrupted battery. The stepping magnet 6will now operate to rotate the wipers 23, 24, 25 step-by-step in theforward direction until they reach the home-posi tion. 'At this positionthe cam 14 will again open the springs 13 thereby opening the returnstepping circuit of the stepping magnet 6. Consequently, the wipers willremain resting in the home-position. The replacement of the receiver atthe called substation effects the release of the connector as is wellknown and need not be discussed.

A brief explanation of the operation of line switch LS may now be givenand for ill) initiate the call, the subscriber at substation AFremoveshis receiver and dials the direc tory number of the substationwith whichconnection is desired. Removing the receiver at substation A places abridge across the lineconductors 2 and 3 and, closes a circuit for theline relay 5 of the line switchLS';

Line relay 5 energizes and places ground on the home-position privatecontact 21, on the lower end of the winding of the switching relay 4-,and on the private conductor 16, at armature 11; and at armaturelZcloses a circuit for the stepping magnet 6. This circuit may be tracedfrom ground on contact 21, wiper 2i, armature 9' and the restingcontact, the working contact and armature l2, interrupter springs 15,through the winding oit thestepping magnet 6 to battery. Switching relayl isshort-circuitcd at this time'by ground on'both ends of its winding.Stepping magnet 6 energizes and, nearthe end of its stroke, opens itsown circuit at the interrupter springs -15. Stepping magnet 6thenreleases and in so doing rotates the switchwipers23, 2 L 25, off thehome-position to the next set of bank contacts. Cam 14 alsowrotates andcloses springs 13, thereby preparing the return stepping circuit tobedescribed later. If the selector accessible at this set of bankcontacts is busy, the private contact engaged by the private wiper 24willbe grounded and the circuit for the stepping relay 6 will again becompleted and the wipers will be rotated to the next set of bankcontacts. This stepping action will continue until the wipers 23, 24;,25 engage a set of contacts connected to an idle selector. It will beassumed that selector S, accessible at bank contacts 26, 27, 28, is thefirstridle selector encountered. Under this conditionthere will be noground on contact 27', engaged by wiper 2 L. Relay 4; being no longershort circuited by ground on both ends of its winding, will be energizedfrom ground by way of a rmat-ure 11 and the working contact, through thewinding otswitching relay l", closed in terrupter springs 15, throughthe winding of the stepping magnet 6 to battery. The

stepping magnet does not energizeat this time on account of the highresistance of relay t. 'Upon energizing,.relay l prepares a holdingcircuit for itself at armaturefi, opens a point in the return steppingcircuit to be described later atarmature 8, and at armatures 7 and 10disconnect-sthe line conductors 2' and 3 from ground and line relay 5and connects them to the'selector S as similarly described in?connection with the description of line switch LS.

The succeeding operations are also similar to those already described inconnection with net is stopped.

the description of LS, and theytalking connection is; established inlike manner \Vhen T the -subscribers.replace their recc-iversat thetermination Of theficonversas tion, the selector switchesareareleased;and

the holding ground removed from conductor 38?. Switching relay 4. Ideenergizes and closes ytheireturn-stepping circuit at arma-, true 8.This circuit maybe traced from groundby wayof armature 1' 1- and therestingconta'ct, closed springs 13,armature 8' and theresting contact,closed interrupter springs 15, through thewinding ofthe stepping magnet6 to battery. The wipers are rotated in a forwarddirection to thehomeposition. At this position the return-stepping circuit is opened atspringslfi by cam 14, thereby preventingfurther movement of the wipers.L 1

Having described; the invention, what is thought new and is desired tohave protected by Letters Patent is set forth in the appended claims; rlVhat is claimed is: c i 1. In a selector switch, a marginal relay,means for partially operating said relay to start the switch, and meansfor completely operating said relay to stop the switch.

2. In a trunk selecting switch, a twostep magnet closed by said relay inits first step andopened inits second, means for operating said relay inits first step to start the switch hunting, and means lIlClUCllHg a-testcircult for preventing the relay from operating in its second step untilan idle trunk is found. i

3. In a trunk selecting. switch, a relay operable, in two stages, amotormagnet having acircuit closed by said relayin its first stage ofoperation, two windings for said relay, meansforenergizing one windingalone tooperate the relay in its first stage, whereby the operation 01.said magnet is initiated, and testing means for energizing the secondwinding also when an idle trunk is found, wherebythe operation of themag- 4. In a rotary line switch, trunk line contacts, a home positioncontact, a test wiper, means including a circuit extending through saidwiper and said home contact for enabling the switch to start hunting,meansin- [eluding a circuit throughgsaid wiper and busy trunk contactsfor continuing the huntingoperation'until an idle contact is found, oiinormal contacts, and acircuitincluding said oft normal contacts "forcausing the switch to. resume its. movement and continue same until saidwiper reaches said home contact again. r

5. In ajtelephone system, a plurality of line switches, each terminatingin a subscribers l1ne,trunk llnesaccessibleto said line switchesin thebanks thereof, means tor indicating a busy or idle condition of saidtrunk lines, an interrupted battery supply common to said line switches,means in each line switch operable from said interrupted battery supplyfor causing said line switch to connect to an idle one or" said trunklines in response to a subscriber initiating a call, and means in eachline switch including said second named means for causing it to restoreto normal position at the termination of a call, said last named meansalso including normally closed switch contacts which are openedresponsive to the selection of an idle trunk. 1

6. In a telephone system wherein electroresponsive means is provided foroperating atrunk selecting switch, a two step marginal relay contacts ofwhich are connected in a first operated position to establish a circuitto said means and in its second operated position to break the saidcircuit.

7 In a telephone system wherein electroresponsive means is provided foroperating a trunk selecting switch, a two step marginal relay connectedin a first operatedposition to establish a circuit to said means, in itssecond operated position to break the said circuit, and in its normalinoperative position to establish a circuit for said means provided theswitch is in any position other than one certain position.

8. In a telephone system wherein electroresponsivc means is provided foroperating a trunk selecting switch, a two step marginal relay contactsof which are connected in a first operated position to establish acircuit to said means and in its second operated position to break thesaid circuit, and means for preventing the operation of said relay intoits second operated position until an idle trunk is reached. l

9. In combination, a motor magnet, a switch controlling the circuit ofsaid motor magnet, means for partially operatingsaid switch to close acircuit to said motor magnet, means moved under the control of saidmagnet to cause the complete operation of the switch to break thecircuit to said motor magnet.

10. In combination, a motor magnet, a switch controlling the circuit ofsaid motor magnet, means for partially operating said switch to close acircuit to said motor magnet, means moved under the control otsaidmagnet causing the complete operation of the switch, means operated whenthe switch is completely operated to break the circuit to said motormagnet, and means effective upon the subsequent release of said switchto cause the second named means to return to its initial position.

11. In a telephone system, a trunk selecting switch including a motormagnet and a relay controlling. the circuit of said motor magnet, meansfor partially energizing said relay to close a circuit for said motormagnet, a trunk selecting wiper moved under the control of said magnet,said wiper causing the complete energization of the relay, and meansoperated when; the relay is completely energized to break thecircuit tosaid magnet. p

12. In a telephone system. a trunk selecting switch including a motormagnet and a relay controlling the circuit of said motor magnet, meansifor partially energizing said relay to close a circuit for said motormagnet, a trunkselecting wiper moved under the control of said magnet,said wiper causing the complete energization'ot the relay, meansoperated when the relay is completely energized to break the circuit tosaid magnet, and means effective upon the deenergization of said relayto cause the wiper to return to its initial position.

13. In a telephone system a line switch including a trunk selectingwiper having a home position, av line relay, a switching relay,a magnetfor moving the wiper, off normal contacts open when the switch is in thehome position and closed when the switch is in any other position, andan operating circuit for said magnet extending when the switch is awayfrom the home position through two branches, one of said branches beingcontrolled through said wiper and including a front contact on the linerelay and back contact on the switching relay, the other branchincluding back contacts on each ofthc two relays and the off normalcontacts. 1

14:. In a lincswitch oi? the homing type, a line relay, a switchingrelay, amotor magnet, a trunk hunting circuit for the magnet effectivewhen the switch is away from the home position, said circuit includingaback contact of the switching relay and a front Contact of the linerelay, and a homing circuit for the magnet including said back contactof the switching relay, and a second back contact oi the switching relayin series.

'15. In a lineswitch of the homing type,

a line relay, a switching relay, a motor mag net, a trunk huntingcircuit for the magnet effective when the switch is in an oft-normalposition, said circuit including a back contact of the switching relayand a front contact of the line relay in series, and a homing circuitfor the magnet including a back contact on the switching relay and aback contact on the line relay in series.

16. In a lineswitch of the homing type, a line relay, a switching relay,a trunk hunting wiper having a home position contact, a circuit for themagnet for initiating the trunk hunting movement of the switch, saidcircuit being controlled over said wiper and the home contact andincluding a back contact on the switching relay anda front contact onthe line relay in series, otiqiorinal contacts, and a homing circuit forthe n1agtrunk hunting movement of the switch, said circuit beingcontrolled over said Wiper and the home contact of the switch andincluding a back contact on the switching relay and a front contact onthe line relay in series, off-normal contacts, and a homing circuit forthe magnet including said off-nor- 1nalcontacts, said back contact ofsaid switching relay and a i ront contact of the line relay.

18. In a rotary line switch, a cut ofi relay, and a circuit for saidrelay extending through two setsof contacts on said relay in i series.

In Witness whereof, I hereunto subscribe my name this 6th dayof May, A.D., 1925.

BERNARD D. WILLIS.

